Drivers of biodiversity change in British alpine habitats

Andrea Britton, Alison Hester, Colin Beale, Richard Hewison & Willie Towers

UK alpine habitats

Wide variety of habitats

Strong oceanic influence

Important role of lower plants

High biodiversity value

Ecosystem services

C storage

Water cycle

Anthropogenic impacts

Local scale drivers:

Recreation impacts

Hiking

Skiing

Grazing

Management

Anthropogenic impacts

Pollutant deposition:

Sulphur

Deposition declining

Persistent effects

Nitrogen

Deposition remains high

Source: ROTAP 2010

Sulphur deposition

Source: www.apis.ac.uk

Anthropogenic impacts

Climate change:

Temperature

Average 1°C rise since 1961

Precipitation

60% increase in winter rainfall

Snowfall

30% reduction in days with snow cover

1961-2004

How has biodiversity responded over the last 40 years?

Alpine vegetation is exposed to multiple drivers of change…

Birse and Robertson Survey 700+ plots recorded 1960-1980

205 plots resurveyed 2004-6

Range of typical alpine communities

Recorded species composition & sward structure

Overall change: plot scale

Mean species richness

increased from 16 to 19

old new

Mean s

pecie

s r

ichness

0

5

10

15

20

25

***

Plot-level diversity

(Shannon) has declined

Old New

Mean S

hannon I

ndex H

'

0.0

0.5

1.0

1.5

2.0 ***

Overall change: landscape scale New sill is significantly lower (P<0.001)

Spatial turnover of composition reduced – more homogeneous

Old data New data

Habitat specific changes Richness change

differs between

higher plants and

bryophytes

Higher plants

increase most in

snowbed and

springs, no change

in fell field

Bryophytes increase

most in fell field,

decline in tall Juncus

grassland Callu

na heath

Vaccinium heath

Racomitrium heath

Fell field

Snowbed

Springs

Grassland

Juncus Grassland

Nardus grassland

Mean c

hange in s

pecie

s r

ichness

0

1

2

3

4Highers

Bryos

Species trends Winners:

Middle altitude, widespread species

Losers:

High altitude, northern species

How do observed changes compare with experimental studies?

Example: Alpine Calluna heath

Changes in survey plots:

Increased higher plant and bryophyte richness

Increased Calluna cover

Reduced lichen cover

Increased sward height

Culardoch long-term experimental site

Nitrogen addition

Warming (open top chambers)

Grazing

Burning

Driver responses – Higher plants

Survey finding: increased

Calluna cover

Experimental response:

Positive response to both N addition and warming

Increased shoot growth

Increased flowering

No change in species

composition (after 10

years)

Year

1998 2000 2002 2004 2006 2008 2010

Me

an

sh

oo

t e

xte

nsio

n (

mm

)

10

15

20

25

30

35

40

0 kg N

10 kg N

20 kg N

50 kg N

Year

1998 2000 2002 2004 2006 2008 2010

Mean s

hoot ext

ensio

n (

mm

)

10

15

20

25

30

35

40

45

-OTC

+OTC

OTC's installed

Driver responses - lichens

Survey finding: decreased

lichen cover

Experimental response:

rapid decline in cover and

richness with N addition

Sensitive to low loads &

concentrations

Lichen abundance also

related to sward height –

indirect effect of climate

and/or grazing

N addition (kg N ha-1 y-1)

0 kg 10 kg 20 kg 50 kg

Lic

hen s

pecie

s r

ichn

ess

0

2

4

6

8

10

Conclusions

UK alpine habitats are changing

Species of sub-alpine habitats are expanding while alpine

specialists decline

Nature of change is habitat specific

Experimental studies show that multiple drivers can contribute

to observed changes

Future studies: avoid considering single drivers in isolation

Acknowledgements

Thank YOU for listening

Scottish Government & DEFRA for funding

Julia Fisher, Dave Riach and Heather Armitage for help with field work